Subsequently, rather arbitrary criteria based on clinical experience for frequency and chronicity were placed in the DSM-IV criteria for BN. There is some question as to whether a person who binges and purges once a week is equally impaired as a person who binges and purges twice a week. Important clinical features of BN are the feeling of lack of control over eating and the regularity of binge eating. Many of these patients are very concerned about body shape and weight, which is another criterion for the diagnosis. However, there appears to be a subgroup for whom bingeing and purging is an addictive phenomena to relieve anxiety (Lynch et al., 2000; Powell and Thelen, 1996). This latter group is not well studied or defined.
It is assumed that patients with a diagnosis of BN are within 10% of normal weight range. If they are below 15% of a normal weight range, they usually meet criteria for AN, binge/purge subtype. To further clarify the diagnosis of BN, two subtypes were defined: the purging subtype, who self-induces vomiting and abuses laxatives, diuretics or enemas and the non-purging subtype, who uses compensatory behaviors to combat caloric intake by exclusively fasting or excessive exercise. Most patients with the non-purging type of BN are in the upper part of a normal weight range or are actually overweight. The criteria for BN will continue to be revised until ongoing studies of the biology of the disorder, including neuroimaging and genetic studies as well as longitudinal course studies, are completed.
Partial Eating Disorder Syndromes
The current DSM-IV diagnostic system recognizes that there are many variants of AN and BN that do not meet the specific criteria for these disorders but involve significant impairment of function. Thus, the diagnostic system simply states that the category of eating disorder not otherwise specified (EDNOS) is for disorders of eating that do not meet those criteria. An example is binge-eating disorder, which is defined as recurrent episodes of binge eating in the absence of the regular use of the inappropriate compensatory behaviors characteristic of BN. The major problem with binge-eating disorder is distinguishing it from the non-purging subtype of BN. It is emphasized that the diagnosis should be considered only when the individual reports a subjective sense of impaired control during episodes of overeating. Many of these individuals are obese and eat throughout the day in addition to their binge-eating episodes. Most have long histories of repeated efforts to diet, and others have given up all effort to diet. According to the DSM-IV, about 30% of individuals in weight control programs will have binge-eating disorder. Other examples of EDNOS are individuals who are within a normal weight range, eat normal size meals and then regularly purge.
Studies of the partial syndrome cases have produced discrepant results. In one study, the severity of eating disorder symptoms in people with partial syndrome cases was as great as or greater than those with full syndrome cases (Martin et al., 2000). In another study, people with partial syndromes or subclinical eating disorders had lower severity scores than those with full syndrome eating disorders (Cotrufo et al., 1998). A third study showed that some individuals, over time, progressed from the less to the more severe disturbances in eating behavior (Shisslak et al., 1995).
Depression is common in both AN and BN. Two-thirds to three-fourths of these patients will have a lifetime history of depressive disorder (Braun et al., 1994; Ivarsson et al., 2000; Wade et al., 2000). In both AN and BN, one-half to two-thirds of patients will have a lifetime history of an anxiety disorder (Braun et al., 1994). Obsessive-compulsive behaviors often develop or become worse as AN progresses in severity. An obsession with cleanliness, an increase in cleaning activities and compulsive studying are commonly observed in these patients. The actual occurrence of lifetime obsessive-compulsive disorder as defined by DSM-IV criteria is only about 20% of patients with AN.
Several studies have shown a greater prevalence of OCD in the first-degree relatives of patients with eating disorders compared to controls (Cavallini et al., 2000; Halmi et al., 1991). A higher morbidity risk for obsessive-compulsive spectrum disorders in the first-degree relatives of patients with eating disorders compared to those of controls has led to the proposal that OCD and eating disorders are phenotype expressions of a common liability. In another family study, the risk of obsessive-compulsive personality disorder was elevated only among relatives of anorectic probands, evidence that these two disorders may have shared familial risk factors (Lilenfeld et al., 1998). Therefore, obsessional personality traits may be specific familial risk factors for AN. One of the common features of obsessive-compulsive personality disorder is perfectionism. In another study, patients with AN had significantly higher perfectionism ratings compared with controls (Halmi et al., 2000). The authors concluded, "Perfectionism is likely to be one of a cluster of phenotypic trait variables associated with a genetic diathesis for anorexia nervosa."